Polymers prepared from monoethylenically unsaturated monomers containing pendant tertiary amino groups are well-known, and have been rendered cationic and water dispersible by neutralization with a solubilizing acid to comprise a portion of an electrocoating bath. The dispersed polymer particles migrate to the cathode when a unidirectional electrical current is passed between the anode and cathode in the aqueous electrocoating bath, and deposit upon the cathode to form a coating thereon.
The co-assigned U.S. Pat. No. 4,198,495 and No. 4,195,147, both by K. Sekmakas and R. Shah, deal with some of the problems of amine-functional cathodic electrocoating compositions, especially from the standpoint of providing a stable aqueous dispersion at a pH value close to neutral.
The amine-functional copolymer systems of the prior art are inadequate because, during polymerization, the amine-functional monomers, which are commonly based on amine-functional derivatives of acrylic or methacrylic acids, tend to homopolymerize and thereby form locally high concentrations of amine-containing groups in portions of the copolymer molecule. These localized concentrations of amino groups tend to make neutralization with solubilizing acid less efficient, and this diminishes the dispersibility of the resultant copolymer in aqueous dispersions which leads to instability in the aqueous electrocoating bath. The method of U.S. Pat. No. 4,195,147 minimizes this inadequacy, but it does not eliminate it completely.